/*
 * Copyright 2021 Shulie Technology, Co.Ltd
 * Email: shulie@shulie.io
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.shulie.surge.data.runtime.disruptor;

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 * Blocking strategy that uses a lock and condition variable for {@link EventProcessor}s waiting on a barrier.
 *
 * This strategy can be used when throughput and low-latency are not as important as CPU resource.
 */
public final class BlockingWaitStrategy implements WaitStrategy
{
	private final Lock lock = new ReentrantLock();
	private final Condition processorNotifyCondition = lock.newCondition();

	@Override
	public long waitFor(long sequence, Sequence cursorSequence, Sequence dependentSequence, SequenceBarrier barrier)
			throws AlertException, InterruptedException
	{
		long availableSequence;
		if ((availableSequence = cursorSequence.get()) < sequence)
		{
			lock.lock();
			try
			{
				while ((availableSequence = cursorSequence.get()) < sequence)
				{
					barrier.checkAlert();
					processorNotifyCondition.await();
				}
			} finally
			{
				lock.unlock();
			}
		}

		while ((availableSequence = dependentSequence.get()) < sequence)
		{
			barrier.checkAlert();
		}

		return availableSequence;
	}

	@Override
	public void signalAllWhenBlocking()
	{
		lock.lock();
		try
		{
			processorNotifyCondition.signalAll();
		} finally
		{
			lock.unlock();
		}
	}
}
